Process for producing phosphoric acid.



F. J. MAYWALD.

PROCESS FOR. PRODUCING PHOSPHORIG AGID..

APPLICATION FILED SEPT. 10, 1902.

902,157. Patented Oct. 27, 1908.

WITNESSES: INVENTOR 97 ll. I V K BY )1 ATTORNEY UNiTnD STATES PATENTorTicE.

PROCESS FOR PRODUCING PHOSPHORIC ACID.

Specification of Letters Patent.

Patented Oct. 27, 1908.

Application filed SeptemberlO, 1902. Serial No. 122,759.

To all whom it'may concern:

Be it known that I, FREDEIHCK J. MAP warn, a citizen of the UnitedStates, residing in Brooklyn, in the county and State of New York, haveinvented a Process of Producing Phosphoric Acid; and I do hereby declarethe following to be afull, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

My invention relates to a process of producing phosphoric acid fromnatural phosphates, such as are known as phosphate rock, and isapplicable to aluminum phosphate, calcium phosphate, and mixtures ofcalcium and aluminum phosphates and calcium, aluminum and ironphosphates. These phosphates having an earthy base of alkaline earth orearthy oXid are all relatively infusible.

The process consists in passing an electric current through a mass ofthe coi mninuted material, and collecting the fumes evolved, preferablyby condensing them to a powder, which is readily soluble in water. Underthe conditions of operation, as hereinafter set forth, the phosphatesimply dissociates and the P 0, distils away, leaving a residue of baseor basic phosphate. The P 0 is collected as such The objects of myinvention are, to produce phosphoric acid in a simple and inexpensivemanner and in a readily soluble form.

In the dravsiings which accompany and form a part of this specification,I illustrate diagrammatically an apparatus which may be used forcarrying out my process.

Said apparatus consists of a crucible 1, which may be of plumbago orgraphite or other suitable material, and may Vided at its bottom with anaperture through which may be inserted a carbon electrode 2. Above thiscrucible is a condensing hood 3 for collecting the fumes evolved andinsaid hood is an aperture through which mav be inserted another carbonelectrode 4. The

hood may be constructed of metal and if radiation to the surroundingatmosphere is not suflicient to keep it cool, it may becooledartificially, as by blowing a blast 'of air upon it.

A dynamo or-other generator 5 is placed in circuit with the carbonelectrodes 2 and 4, and in this circuit there may be anadjustableresistance 6.

be pro- I In carrying out the process, the material to be used isplaced, preferably in a finely pulverized condition, within thecrucible, retort, furnace or other object within which the process isconducted. A trace of carbon in the material will often aid in theevolution of the phosphoric acid if the material be diflicult todissociate. But the addition of carbon is not ordinarily necessary. Iordinarily employ a current of from 40 to volts. The voltage is higherat the beginning of the operation, but as the mass becomes hot thevoltage will fall of itself.

It is preferable to employ a short are, the carbon electrodes beingplaced close together, as there is then less tendency to producephosphorus than when a long arc is used. But I have found resistanceheating to be effective; the resistance heating being effected byseparating the carbons when the mass within the crucible is hot, so that'no distinct arc is produced but the electric current permeates the massof granular material between the two electrodes. temperature of the massis kept below the melting point thereof, as I have found that if themass be heated to the melting point it is impracticable to drive off allof'the phosphoric acid. But when not heated to the melting point, themass remains in a porous condition, which permits free escape ofphosphoric acid.

A slight amount of air may be permitted to enter the crucible or furnaceto oxidize any phosphorus that may be formed. Such air may be introducedthrough a slight space left between the crucible and condensing hood orby other suitable means.

The result of the passage of the electric current is to dissociate thephosphate and liberate the phosphoric acid in a anhydrous form from thematerial treated, and the fumes of this anhydrous acid or P 0 condenseupon the hood 3 as a powder which is readily soluble in cold water. Fromtime to time the hood 3 may be removed and the powder which thuscollects dislodged therefrom. I

I do not limit myself to the use of the particular apparatus shown inthe drawings, or to the use of any particular apparatus, or to anyparticular material from which to form the crucible or furnace, or theelectrodes, or the condensing hood; nor do I limit myself to anyparticular form of condensing apparatus, nor to any particular In anycase, the

strength of current. Likewise, the process may e applied to theextraction of phosphoric acid from other salts of said acid than areabove specified.

Having thus completely described my invention, What I claim and desireto secure by Letters Patent is:

1. The process of treating phosphates which consists in producing a lowpotential are in a granular mass of phosphates having an earthy base andheating such phosphates to a dissociating temperature, therebydecomposing the same into phosphoric oxid and base, and in collectingthe fumes of phosphoric oXid as such.

The process of treating phosphates which consists in. subjecting agranular mass of phosphates having an earthy base to heat. and theaction of a short electric arc and heating such phosphates to adissociating temperature, thereby decomposing the same into phosphoricoxid and a basic residue, and in collecting evolved fumes of phosphoric0Xi(l.

3. The process of treating phosphates which consists in subjecting agranular mass of relatively infusible phosphates to heat and the actionof a short electric arc While permitting access of air to such mass, andheating such phosphates to a dissociating temperature, therebydecomposing said phosphates into phosphoric oxid and a basic residue,and in collecting the evolved fumes of phosphoric oxid.

4:.- The. process of treating phosphates Which consists in subjecting agranular mass of relatively infusible phosphates to the action of theare produced by an electric current not materially exceeding 60 volts inpotential, and heating such phosphates to a dissociating temperature,thereby decomposing said phosphates into phosphoric oxid and a basicresidue, and in collecting the fumes of phosphoric oxid produced.

5. The process of treating phosphates which consists in initiallyheating a granular mass of relatively infusible phosphates by means of ashort'electric are produced by an electric current not materiallyexceeding- (30 volts in potential, continuing the heating by passing alow potential current through said granular mass and heating suchphosphates to a dissociating temperature thereby decomposing the sameinto phosphoric oxid and a basic residue, and in collecting the fumes ofphosphoric ,oxid

' produced.

In testimony whereof I affix my signature, in the presence of twowitnesses.

FREDERICK J. MAYVALD.

'VVitnesses H. M. NIARBLE, A. H. PERLES.

